Seeding machine for planting multiple seed varieties and method of calibrating same

ABSTRACT

A seeding machine, such as a row crop planter, is described which is adapted to switch between two or more seed varieties as the machine traverses a field. The control system uses a programmed quantity of seed representing a number of seeds in the seed meter that need to be substantially consumed once the flow of a first seed variety is stopped before introducing a second seed variety to minimize seed mixing. The seed quantity can be determined by a calibration process or published from the manufacturer or third parties. The seed quantity can also be part of a seeding prescription that includes assignment of where each seed variety is to be planted in a field. The seed quantity and the distance traveled to empty the meter can be used to optimize the planting operation including the machine direction which can also be part of the prescription.

FIELD

This disclosure relates to seeding machines such as row crop plantersadapted to plant two or more seed varieties within a field and inparticular to the control of such a machine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of a planter illustrating one row unitand two seed supply tanks of a seed delivery system;

FIG. 2 is a sectional view of a vacuum seed meter;

FIG. 3 is a schematic diagram of a controller;

FIG. 4 is a top view of a field map;

FIG. 5 is a top view of the field of FIG. 4 illustrating pixels for aseeding prescription;

FIG. 6 is a flow chart of the control process;

FIG. 7 is a three dimensional graph illustrating variation in theprogrammed quantity of seed in the seed meter based on attitude of theplanter;

FIG. 8 is a plan view of a field illustrating variety prescriptionoptimization;

FIG. 9 is a plan view of a field illustrating a planter Common VarietyArea;

FIG. 10 is a plan view like FIG. 9 illustrating an alternative CommonVariety Area for a planter;

FIG. 11 is a plan view of a field illustrating another varietyprescription optimization including a path plan for the planter;

FIG. 12 is a plan view of a field illustrating another varietyprescription optimization including a path plan for the planter tominimize variety switching; and

FIG. 13 is a plan view of a field illustrating areas of a field whereseed varieties are mixed when a seed variety switch is made with asingle gate switching mechanism.

DESCRIPTION

Most crop production is carried out by seeding an entire field with oneseed variety. However, sufficient agronomic data is now available toutilize site specific planting prescriptions that use two or more seedvarieties in a given field to increase yields. Various factors are usedto determine the best variety for a given location. One area of a fieldmay be lower and typically wetter than other areas. The increasedmoisture alone may suggest a different seed variety in that location. Inaddition, the moisture may result in increased weed or pest pressure inthat location necessitating other varieties with resistance to thosepressures. To plant the field most efficiently with parallel back andforth passes, and to plant with multiple site specific varieties, it isnecessary to switch back and forth between varieties numerous timesbased on the location of the machine in the field.

With reference to FIG. 1, a seeding machine, in the form of a row cropplanter 20, is shown which is capable of switching between seedvarieties without stopping the machine. Planter 20 is equipped withmultiple planting row units 22, only one of which is shown. Row unit 22is only one example of many different types of row units that can beused to plant seed. Row unit 22, as shown, includes an opener 24 thatforms a shallow furrow in the soil as the machine traverses a field.Gauge wheels 26 control the depth of the furrow. A seed meter 28 metersseed to deliver individual seeds sequentially to a seed tube 30 thatdirects the seed to the furrow beneath the meter. A closing wheel orother device 32 trails behind and covers the deposited seed with soil.Each row unit 22 is mounted to the machine frame 34. Multiple row units22 are mounted to the frame 34 such that multiple parallel rows areplanted with each pass of the machine through a field.

Each seed meter is equipped with a small seed hopper 40 commonlyreferred to as a mini-hopper. Seed from two or more tanks 42, 44 isdelivered to the mini-hopper pneumatically through tubes 46, 48.Alternatively, the mini-hopper could be eliminated and the tubes 46, 48connected directly to the meter housing. A tube 46 extends from tank 42to the mini-hopper 40 and a tube 48 extends from the tank 44 to themini-hopper 40. Each tank 42, 44 carries a different seed variety suchthat each variety is delivered to the each mini-hopper. The tanks andtubes are part of a pneumatic seed delivery system 50 such as thoseshown in U.S. Pat. Nos. 6,609,468; 6,688,244; and 7,025,010,incorporated herein by reference. Seed delivery system 50 also includesa fan 52 to provide the air stream to convey the seed through the tubes46, 48. In place of the seed delivery system 50, the planter could beequipped with larger hoppers on each row unit to supply the seed to eachmeter.

Seed meter 28 is shown in greater detail in FIG. 2. The meter 28 is avacuum seed meter which operates with a pressure differential to selectindividual seeds for delivery to the seed tube 30. While the meter 28 isa vacuum meter, other pressure differential meters use a positivepressure instead of vacuum. While a pressure differential meter providessome advantages described below, a mechanical meter, such as a fingerpick-up meter may be used as well. Meter 28 includes a housing 56. Aseed disk 58 divides the interior of the housing into two chambers, aseed chamber 60 and a vacuum chamber 62. The seed disk 58 is mounted inthe housing for rotation about an axis 64. The meter is a vacuum seedmeter such as the meter shown in U.S. Pat. No. 5,170,909 incorporatedherein by reference.

The tubes 46, 48 pass through the mini-hopper and terminate near thebottom of the hopper, at a switching mechanism 68. The switchingmechanism 68 may be of the type shown in U.S. Pat. No. 6,193,175,incorporated herein by reference. The switching mechanism 68 has tworotary gates 69, 70 each having an opening 71 there through for passageof seed. Gate 69 is rotated by an actuator 72 while gate 70 is rotatedby an actuator 73. As shown in FIG. 2, the openings 71 of both gates arealigned with the tube 46 allowing seed variety A from tube 46 to enterthe meter housing. The gates can both be rotated to align the openings71 with the tube 48 allowing seed variety B from tube 48 to flow intothe meter housing. Since each gate is separately controlled, one gatecan close tube 46 while the other gate closes tube 48 to prevent bothseed varieties from entering the meter housing. This allows the seedvariety in the meter to be exhausted before introducing the othervariety as described below. The illustrated switching mechanism 68 isonly one example of a switching mechanism, other mechanisms can be used.When the switching mechanism 68 opens either tube 46 or 48, seed fromthe respective tank is allowed to flow into the seed chamber of themeter housing and accumulate in a seed pool 76 in the housing.

The meter housing 56 includes a hose fitting and opening 80 to thevacuum chamber 62 on the side of the seed disk opposite the seed pool76. The fitting is connected to a hose, not show, which is coupled tothe inlet side of a vacuum fan to produce a vacuum in the chamber 62.The seed disk 58 has a circular array of apertures 82 extending throughthe disk near its periphery. The apertures 82 extend through the diskfrom the seed side to the vacuum side. As the seed disk rotates, thevacuum on one side of the disk causes individual seeds to be adhered tothe disk on the seed side, at the apertures 82 as shown by seeds 84 atthe top of the disk in FIG. 2. After the seed is rotated to the releaselocation, the vacuum is cut-off, allowing the seed to fall sequentiallyinto the seed tube 30 to the furrow in the soil. Other types of seedmeter can also be used including, but not limited to, positive pressuremeters or mechanical meters such as a finger pick-up meters, etc.

A controller 86 for controlling the function of the planter 20 is shownin FIG. 3. Controller 86 is only an example of a controller architectureto illustrate the control functions. The hardware architecture may vary.Controller 86 includes a central processing unit, CPU, 88 and a variablerate/variety controller, VRVC, 90. The VRVC 90 controls the operation ofthe actuators 71, 72 to rotate the gates 69, 70 to determine which seedvariety flowing into the meter housing. VRVC 90 also controls therotation speed of the seed disk 58 to determine and vary the seedapplication rate, that is, the number of seeds per unit of area, e.g.seeds per acre. Both the CPU 88 and VRVC 90 receive vehicle speed inputfrom true ground speed sensor 92. Further inputs to the CPU includemachine location data input 94 such as GPS data providing geo-referencedlocation of the machine. A memory card 96 with prescription data from ahome office computer 98 or other computer provides data to the CPU ofwhich variety of seed is to be planted at each location in the field andat what application rate. A wireless input device 100 may also beprovided to transmit a prescription wirelessly to a memory device 102. Avisual display 104 is provided to deliver information to the operator.The display may be touch screen to allow for user inputs and/or otheruser input devices 106 may be provided such as knobs, switches,keyboard, voice commands, etc.

A field map is shown in FIG. 4 wherein locations in a field 110 forplanting each of two seed varieties A and B are indicated. Most of thefield is to be planted with variety A while the areas within theirregularly shaped polygons 112, 114 are to be planted with variety B.Polygon 112 is contained within the field 110 while polygon 114 isdefined in part by the boundaries of the field 110. The controller 86can control the variety based on where the planter 20 is located withrespect to the boundaries of the two polygons 112, 114. If the planteris outside the polygons, plant variety A and if the planter is insidethe polygons, plant variety B. Alternatively, with reference to FIG. 5,the field can be divided into a number of small rectangular areas orpixels. Each pixel is geo-referenced and has a seed variety A or Bassigned thereto and a seeding rate in a seeding prescription. When theplanter is in a given pixel, it plants the variety assigned to thatpixel. With either type of field designation, the controller 86 must beprogrammed to look ahead at the current path to anticipate changes inseed variety as described below. While two seed varieties are described,it will be apparent that the more than two varieties can be planted in agiven field with equipment so equipped.

When switching from one variety to another, it is desirable to minimizethe mixing of the two seed varieties so that when switching from varietyA to variety B there is only a small region in the field where the twovarieties are mixed together before planting solely variety B. Tominimize mixing of varieties, gates 69 and 70 are rotated to positionsclosing both tubes 46 and 48. This allows the seed in the seed pool 76to be substantially exhausted before opening tube 48 to allow variety Bto flow into the meter. While crisp switch in varieties may bepreferred, some mixing of seed is better than allowing the meter to runcompletely empty and leaving an area in the field not planted. When thetractor 116, FIG. 4, approaches the boundary of the polygon 112, thecontroller 86 must stop variety A from flowing into the meter asufficient distance before reaching the polygon to allow seed A to bedepleted and then introduce seed B into the meter just in time to beginplanting seed B at the boundary of the polygon. To do so, the controllerneeds to know the number of seeds in the seed pool 76 at the time whenstopping seeds of variety A from flowing into the meter. Using thenumber of seeds, also referred to as the size of the seed pool, togetherwith the seeding rate or rates between the current location and thepoint X on the polygon boundary where the planter needs to beginplanting seed B (FIG. 4), the controller determines a point Y at whichto stop the supply of seed A into the meter.

To determine the location Y, the size of seed pool 76 must be known. Thecontroller is adapted to utilize a programmed quantity of seed in theseed pool 76 for making this calculation. The programmed quantity ofseed is based on the seed size and the geometry of the seed meterhousing. Seeds of variety A may be of a different size than the seeds ofvariety B. Furthermore, due to the physical geometry of the meter, forexample, the different locations of the lower ends of the tubes 46 and48 supplying the seed to the meter, the programmed quantity of seed inthe seed pool may be different for each seed variety. One way to knowthe seed pool size is to perform a calibration process as part of aplanter set-up. The calibration process includes the steps of fillingthe meter housing with seed A, operating the seed meter at least untilall the apertures on the seed disk are filled with seed and seed beginsto fall through the seed tube as detected by seed sensor 118 on the seedtube 30. The switching mechanism 68 is then moved to a position closingboth tubes 46 and 48, stopping the supply of additional seed A to themeter. The meter continues to operate until the seed pool in the meteris exhausted while the seed sensor 118 counts the number of seedsdelivered by the seed meter. The number of seeds counted is the “SeedCount to Empty” for variety A.

To avoid running the seed meter completely empty of seed when switching,some minimum number of seeds, for example twenty seeds, needs to bepresent in the meter at all times. The Seed Count to Empty, less theminimum number of seeds, is the programmed quantity of seed supplied tothe controller for calculating when to stop supply of seed A during aswitch. Once the programmed quantity of seed is determined for varietyA, the meter is then filled with seeds of variety B and the calibrationprocess repeated. The supply of seeds B to the meter is stopped and themeter is run until empty while counting the number of seeds. The “SeedCount to Empty” for variety B less the minimum number of seeds, becomesthe programmed quantity of seed for variety B.

If the seed meters of the planter are driven by motors, such as electricor hydraulic motors, the calibration process described above can beperformed when the planter is static before operating in a field.Alternatively, and for all planters having meters driven by groundwheels, the planter can be operated in the field for the calibrationprocess. In doing so, one row is used for the calibration where supplyof seed A is stopped to allow the size of the seed pool to be counted.Since the meter is run empty during the calibration process, there couldbe a one time, one row gap in planting of several feet for each variety.

The programmed quantity of seed can also be determined without runningthe meter to empty by sensing operational parameters of the meter thatindicate it is near empty. As the seed pool nears empty, the disk willtravel through a smaller number of seeds. Before the meter completelyempties, the frequency of seed skips, as detected by the seed sensor118, will increase. The count of seeds up to the time when the skipfrequency increases can be used as the programmed quantity of seed forthat variety. Likewise, as the seed pool becomes smaller, more apertureson the seed disk will be open between the release point and the seedpool, due to the smaller size of the seed pool. The additional openapertures will result in a drop of vacuum pressure in the vacuumchamber. When a decrease in the vacuum pressure is detected by pressuresensor 120, the seed count reached up to that point becomes theprogrammed quantity of seed. The pressure in a positive pressure meterwill also likely decrease as the seed pool size deceases to near empty.When either of these operational parameters show a change that indicatesthe seed pool is near empty, the seed count up to that point in time canthen be used as the programmed quantity of seed. It is possible thatother operational parameters can be used to detect a near emptycondition of the meter. The above mentioned minimum number of seedsideally is the number of seeds needed in the meter to avoid anyoperational parameter from indicating a decline in meter function.

The programmed quantity of seed can also be published data that theoperator then inputs into the controller 86 through one of the inputdevices 104 or 106. The data can be published following testing by theplanter manufacturer, the seed company, a third party testing service,etc. The seed company could test and publish, for each seed variety, atable of programmed quantity of seed values for common planter models.It is expected that seed companies or third party agronomists willprepare and supply to a producer a prescription of the seed varietiesand seeding rates for a given field. The prescription can include theprogrammed quantity of seed to be used in operating the planter.

The planter is operated using the programmed quantity of seed todetermine when to stop supplying one seed variety to the planter beforeintroducing the next seed variety into the meter when making a switchbetween varieties. The controller uses the programmed quantity of seedand the application rate to determine a “Distance to Empty.” Thecontroller is also looking forward along a current path and determines a“Distance to Switch” representing the distance of the planter from thepoint X on the boarder of the polygon 112, FIG. 4. As long as theDistance to Switch is greater than the Distance to Empty, more seed thanthe programmed quantity of seed in the meter is needed to plant to theswitch point. When the Distance to Switch equals the Distance to Empty,the planter is at point Y. The supply of seed variety A to the meter isstopped and the programmed quantity of seed in the meter is the amountof seed needed to plant from the point Y to the point X where the switchneeds to occur. When the planter reaches point X, the number of seeds inthe meter should be equal to the minimum number of seeds. At this point,seed of variety B is supplied to the meter.

To ensure minimal mixing of varieties and to ensure proper operation ofthe seed meter, it is recommended to monitor planter performance duringswitching operations and make adjustments to the programmed quantity ofseed as necessary. This is done by counting the seeds delivered by themeter once seed supply to the meter is stopped to verify that theprogrammed quantity of seed is accurate. If not, the programmed quantityof seed is adjusted to a new value. For example, if during operation,there is a decrease in the planter performance as detected by theoperational parameters mentioned above before the programmed quantity ofseed has been delivered by the meter, this indicates that the programmedquantity of seed is greater than the actual quantity of seed in themeter. When the controller detects a decrease in planter performance,the count of seeds at the time of the change in the operationalparameter becomes the new programmed quantity of seed. However, if thereis no change in the operational parameters at the time when the meter isnear empty, it may indicate that the programmed quantity of seed is lessthan the actual number of seeds in the meter. This would result in moremixing of seed then desired at the switch. If this occurs, thecontroller can increase the programmed quantity of seed slightly beforefor the next switch to arrive at a more precise number of the actualseeds in the meter. For instance, the programmed quantity of seed may beincreased one percent for the next switch and then the operationalparameters monitored to determine if the new programmed quantity of seedis correct. In this manner, the controller gradually reaches a moreprecise programmed quantity of seed.

The process for determining when to operate the switching mechanism isshown in FIG. 6 Starting with box 200 the controller calculates theDistance to Empty based on the programmed quantity of seed and theapplication rate or rates between the current location and the switchpoint X. In box 202 the controller calculates the Distance to Switch,that is, the distance between the current location and the boarder ofone of the polygons 112 or 114 along the current path. In diamond 204the controller determines if the Distance to Empty is less than theDistance to Switch. If no, the current quantity of seed in the meter isnot enough to reach the switch point, more seed is needed. Operation ofthe planter continues and the controller returns to box 200 and repeatsthe process. If yes, the quantity of seed in the meter is sufficient toreach the switch point without any additional seed. The controller movesto box 206 and actuates the switching mechanism 68 to close both tubesand stop flow of seed into the meter. The meter then begins to empty andthe seeds dispensed are counted, box 208.

The controller then determines if the current seed count is less thanthe programmed quantity of seed in diamond 210. If yes, there shouldstill be seed in the meter. However, it is possible the programmedquantity of seed was too high. To check for this, the controller, in box212 checks to see if any operational parameter of the meter indicates itis close to empty. If no, the controller returns to diamond 210. If yes,this indicates that the programmed quantity of seed was greater than theactual number of seeds in the meter and the meter is almost empty eventhough the seed count is less than the programmed quantity of seed. Ifthis occurs, the controller moves to box 214. There, the switchingmechanism 68 is actuated to open the other variety to the meter and theprogrammed quantity of seed for the previous variety is changed to thecurrent seed count. The controller then returns to the beginning at box200.

If in the diamond 210 the seed count is not less than the programmedquantity of seed, than the planter has used all the programmed quantityof seed and the planter should be at the switch point X. The controllermoves to diamond 216 to determine if the operational parameters areindicating that the meter is close to empty. If yes, this confirms thatthe programmed quantity of seed is an accurate number. The controllermoves to box 218 and actuates the switching mechanism 68 to open thesupply of the next variety of seed to the meter. The controller thenreturns to box 200 to look for the next switch. If there is no decreasein any operational parameter in box 216, the controller moves to box220. There the controller also actuates the switching mechanism 68 toopen the supply of the next variety of seed to the meter but since theoperational parameters do not indicate the meter is close to empty, thecontroller slightly increases the programmed quantity of seed for thenext switch, for example, increase the programmed quantity of seed by1%. The controller then returns to box 200 for the next switch. Thecontroller thus fine tunes the programmed quantity of seed to achieve anaccurate number of the seeds in the meter for each variety.

The seed pool size can also change based on the attitude of the planter.Using machine attitude data from an accelerometer 122 mounted to theplanter 20, the programmed quantity of seed can be adjusted. Theadjustment can be made based on known test data that shows a percentageincrease or decrease in the seed pool size based on the angle ofinclination of the planter both in left or right roll and forward orbackward pitch. An example of variations in the programmed quantity ofseed due to machine attitude is shown in FIG. 7. In the absence of testdata to adjust the programmed quantity of seed, the operationalparameters as mentioned above can be used to detect variations in thenumber of seed in the seed meter for variations in the machine attitudeand make adjustments to the programmed quantity of seed based on machineattitude. As the machine attitude changes, the controller determines anew Distance to Empty based on the changing programmed quantity of seed.

For planters having a common seed meter used for all seed varieties andwhere switching between varieties is accomplished by changing thevariety of seed that is supplied to the meter, the programmed quantityof seed is a parameter needed to develop a seed variety prescription.The programmed quantity of seed determines a minimum distance that mustbe covered with a given seed variety before switching to anothervariety. For example, once a switch has been made from variety A tovariety B and the seed meter is filled with seed B, the planter willhave to travel a Distance to Empty to consume seed B in the meter beforethere can be a switch back to seed variety A. The prescription shouldconsider the programmed quantity of seed and the Distance to Emptycalculated therefrom in determining the prescription. The effect of theDistance to Empty can be used one of two ways. If the distance to becovered with the second seed variety is smaller than the Distance toEmpty, the prescription could simply not make the switch to the secondseed variety. Or, the second seed variety could be used over a largerarea then desired for the prescription by overlaying a portion of thesecond variety on an area where the first variety would be desired.Preferably, the prescription would center the second variety over thearea desired so that switching points would be even on both sides of athe area for variety B. See FIG. 8. There a field 130 mostly plantedwith a variety A. The field has a narrow band 132 to be planted invariety B. The width of the band 132 is narrower than the minimumswitching distance of the planter shown by the rectangular blocks 134.If each switch is accomplished as the planter reaches the band 132, theblocks planted with variety B would be staggered as shown at the top ofthe FIG. 8 where the arrows show the planter travel direction. However,if the prescription takes into consideration the size of the minimumswitching distance, the blocks 134 can be centered on the band 132 asshown by the three blocks near the bottom of FIG. 8.

The Distance to Empty, which is measured in planter travel distance, islikely a different number than the machine width that is capable ofseparate control. Thus, for any given location of the planter 20 andtractor 116 in a field, there is a field area, forward of the planterknown as a Common Variety Area 150, which must be planted with thecurrent seed variety in the meter. The length of the Common Variety Areais the Distance to Empty and the width is the narrowest area of theplanter capable of separate control. In the example of FIG. 9, the widthof the Common Variety Area is the width of the planter. If smallersections of the planter can be separately controlled, for example, threesections, there are three Common Variety Areas, 150A, 150B and 150Cextending forward from the planter as shown in FIG. 9. If each row unitis separately controlled for seed variety, then there would be aseparate Common Variety Area for each row unit. The Common Variety Areamoves forward with the planter as the planter moves across the field.

To optimize a variety prescription for a given field, the prescriptionshould consider the size of the Common Variety Area. This was done asshown in FIG. 8 by centering the Common Variety Area, shown by theblocks 134 over the band 132. Furthermore, an optimized prescription caninclude a path plan for the planter taking the Common Variety Area intoconsideration. For example, with reference to FIG. 10, the field 160 hasa gulley 162 running across the field that is generally wetter and couldbenefit from a different variety from the rest of the field. But thewidth 164 of the gulley area is shorter than the length of the CommonVariety Area 150 of the planter in the usual direction of travel forplanting, side-to-side as viewed in FIG. 11. The prescription may beoptimized, however, by planting top-to-bottom so that the length of theCommon Variety Area 150′ can be better aligned with the gulley area 162.Harvesting machine efficiency should also be considered in planter pathplanning. Changing the planting direction may be most practical when thecrop is to be harvested with a row-insensitive harvesting machine.

Optimization of the prescription occurs when the area of the field thatis not planted with the optimal variety in minimized. Since the CommonVariety Area is not always the same dimension in both directions, anoptimized prescription needs to include a planter path plan. The pathplan can be executed automatically if the tractor is equipped toautomate the tractor steering or the path plan can be shown to theoperator for manual driving of the tractor. For automated control, theCPU 88 can be adapted to communicate with a tractor guidance controller128 adapted to receive detailed path plan instructions for automatedguidance of the tractor 116. The path plan may be as simple as whichdirection to plant the field as shown in FIG. 11. In this case, thecontroller displays on the display 104 the desired direction forplanting of the field.

An optimized prescription with a path plan may be accomplished byplanting all or substantially all of the area requiring one varietybefore switching to the other variety and planting the remainder of thefield. This prescription may be optimized to minimize the number ofswitches. For example, with reference to FIG. 12 a field 170 is shown,most of which is planted with variety A. One corner area 172 is plantedwith variety B. The area 172 is planted first along the path shown bythe arrows 174 with the planter turning in the headland 176 at the endof the field and turning at the other end outside the area 172. Theheadland 176 can be planted before or after the back and forth passes inthe area 172. After area 172 is planted, one variety switch is made andthe remainder of the field is planted with variety A. This can beaccomplished with an internal headland area 178 surrounding the area172. In this headland area, the planter is turned when making the backand forth passes as shown by the arrows 180. With such a plantingpattern, the headland 178 would need to be harvested first before theback and forth harvesting of the remainder of the field.

The programmed quantity of seed has been described as the seed in themeter of a first variety that needs to be consumed before introductionof a second seed variety when making a switch in seed varieties tominimize mixing of seed varieties. The use of two gates 69, 70 in theswitching mechanism 68 allows for both seed varieties to be stoppedallowing the programmed quantity of seed in the meter to be consumed. Ifthe switching mechanism only had one gate that has two positions, afirst position allowing the first seed variety to flow into the meterand the block flow if the second seed variety and a second position thatallows flow of the second variety while blocking flow of the firstvariety there would be no opportunity for blocking the flow of bothvarieties for a time to substantially empty the meter. The programmedquantity of seed however, can still be used with such a switchingmechanism to at least control where in the field the mixed seed isplanted. With a single gate switching mechanism, when the gate switchesfrom variety A to variety B, there will be a programmed quantity of seedof variety A in the meter. At the switch, A is stopped and B isintroduced into the meter along with the seed A. The seeds will mix andthere will be a region in the field planted with the mixture of seed.Eventually, seed A in the meter will be completely consumed and theplanter will only be planting seed B. The mixed seed area is shown asthe hatched area 240 in FIG. 12 where the planter, when approachingswitch point X switches the gate ahead of the point X such that whenpoint X is reached, the planter is planting seed B at a specified levelof purity, for example, at least 95% of seeds planted are seed B. Byusing the programmed quantity of seed and with testing knowledge fromthe seed meter, the length of the mixed seed area 240 can be determined.The mixed seed area 240 in FIG. 12 is located in the area of seed A suchthat the area in the polygon 112 will be planted with the desired purityof seed B. Alternatively, the mixed seed area 240′ could be locatedinside the polygon 112 if desired. In yet another alternative, the mixedseed area 240″ can straddle the boarder of the polygon 112. In someprescriptions, it may not matter where the mixed seed area is planted.But in some prescription, it may be important that within the polygon112, the seed must be seed B. In such a case, the prescription caninclude the location of the mixed seed area and the controller isoperated in accordance to make the switch such that the mixed seed areais on the proper side of the polygon 112.

Control of the switching of seed varieties has been described in thecontext of the programmed quantity of seed which is the quantity of heldin the seed puddle or the seed in the seed puddle minus a minimum amountof seed that must be in the meter for proper functioning. The programmedquantity of seed could be used to derive a time or distance traveledfrom when the first seed variety is shut-off until the next variety issupplied to the meter. Time and distance can be determined from theprogrammed quantity of seed and the seeding rate and machine travelspeed.

While the planter has been described in the context of applying seed,the above aspects can also apply to the application of chemicals such asfertilizers, pesticides, herbicides, etc. Different chemicals can beapplied to different locations in the field and at different rates. Thewords “seed” and “seed variety” should be broadly construed in theclaims that follow to include not just seeds but different fertilizertypes and other chemical types applied to a field.

Having described the preferred embodiment, it will become apparent thatvarious modifications can be made without departing from the scope ofthe invention as defined in the accompanying claims.

What is claimed is:
 1. A seed distributing machine comprising: a seedmeter having a housing adapted to hold a pool of seed to be singulatedand delivered sequentially; a seed sensor adapted to generate a signalfor each seed delivered by the meter and passing the sensor, a seeddelivery system to provide at least two different varieties of seed tothe meter, the seed delivery system having a switching mechanism tochange from a first variety of seed to a second variety of seed beingdelivered to the meter housing; a controller adapted to operate theswitching mechanism to control which seed variety of the first andsecond seed varieties is delivered to the meter based on the location ofthe machine in a field wherein the controller is adapted to stopsupplying a first seed variety to the meter before supplying a secondvariety to allow for substantial consumption of the first variety ofseed in the seed pool prior to supplying the second variety of seed tothe seed meter, the location of the machine in the field where supply ofthe first variety of seed to the meter is stopped is based on aprogrammed quantity of seed and the seeding rate wherein the controlleris adapted to determine the programmed quantity of seed in the seed poolfor each variety of seed during a meter calibration process.
 2. The seeddistribution machine of claim 1 wherein the meter calibration processincludes the steps of filling the meter housing with a first variety ofseed, operating the seed meter, stopping the supply of the first varietyof seed to the meter, continuing to operate the seed meter until theseed pool in the meter is exhausted while counting the number of seedsdelivered by the seed meter after the supply of seed to the meter hasbeen stopped wherein the number of seeds delivered by the seed meterafter stopping the supply of the first seed variety to the meter is theprogrammed quantity of seed.
 3. The seed distribution machine of claim 2wherein the calibration process is performed while the machine isstationary.
 4. The seed distribution machine of claim 3 wherein duringthe calibration process seed from the seed meter is collected for reuse.5. The seed distribution machine of claim 2 wherein the calibrationprocess is performed while the machine is operating in a field plantingseed.
 6. The seed distribution machine of claim 1 wherein the metercalibration process includes the steps of filling the meter housing witha first variety of seed, operating the seed meter, stopping the supplyof the first variety of seed to the meter, continuing to operate theseed meter until a seed meter operational parameter indicates the seedmeter performance has degraded indicating that the seed pool has beensubstantially depleted while counting the number of seeds delivered bythe seed meter after stopping the supply of seed to the meter whereinthe number of seeds delivered by the seed meter between stopping thesupply of the first seed variety to the meter until meter performance isdegraded is used as the programmed quantity of seed for the firstvariety of seed.
 7. The seed distribution machine of claim 6 wherein theoperational parameter is an increase in the number of seed skips by themeter as detected by the seed sensor.
 8. The seed distribution machineof claim 6 wherein the seed meter is a pressure differential meter andthe operational parameter is a change in the seed meter pressuredifferential.
 9. The seed distribution machine of claim 6 wherein theseed meter is a vacuum seed meter and the operational parameter is adecrease in the seed meter vacuum level.
 10. In a seed meter having ahousing adapted to hold a quantity of seed in a seed pool, a method ofcalibrating the seed meter to determine the number of the seeds in theseed pool, comprising the steps of: supplying the meter housing with afirst variety of seed to form the seed pool; operating the seed meter;stopping the supply of the first variety of seed to the meter; andcontinuing to operate the seed meter until the seed pool in the meter isexhausted while counting the number of seeds delivered by the seed meterafter stopping the supply of seed to the meter wherein the number ofseeds delivered by the seed meter after stopping the supply of the firstseed variety to the meter is the programmed quantity of seed.
 11. In aseed meter having a housing adapted to hold a quantity of seed in a seedpool, a method of calibrating the seed meter to determine the number ofthe seeds in the seed pool, comprising the steps of: supplying the meterhousing with a first variety of seed to form the seed pool; operatingthe seed meter; stopping the supply of the first variety of seed to themeter; continuing to operate the seed meter until a seed meteroperational parameter indicates the seed meter performance has degradedindicating that the seed pool has been substantially depleted whilecounting the number of seeds delivered by the seed meter after stoppingthe supply of seed to the meter.
 12. The method of claim 11 wherein theoperational parameter is the number of seed skips of the meter asdetected by the seed sensor.
 13. The method of claim 11 wherein theoperational parameter is a change in a pressure differential in the seedmeter.